Conventionally, a going barrel for a timepiece movement includes a drum, in which a barrel spring is assembled, wound around a barrel arbour. This barrel spring, generally spiral-shaped, is hooked or fixed to a first peripheral end inside said drum. It is hooked or fixed to a second central end, either to said barrel arbour, or to a core which is coaxial to said barrel arbour, and at least partially guided thereon.
The barrel pivots relative to a bottom plate or barrel bar, on the barrel arbour or the core, in jewels or guide members of the bottom plate or bar.
The barrel is closed, to confine the spring, either by a cover fixed to the drum by clips or other means, or by a ratchet, which is rotatably integral with the barrel arbour or the core depending on the particular case, and thus also forms a cover.
Few configurations permit both automated assembly and easy removal of the barrel from the movement during a maintenance operation.
In the first case where the cover is fixed to the drum and independent of the ratchet, it is impractical to secure the ratchet, generally using screws, in an automated manner. If it is necessary to remove the barrel, for example in the event that the spring breaks, the timepiece movement incorporating the barrel has to be largely dismantled.
In the second case, where the ratchet alone closes the barrel, it is only the barrel spring itself that securely holds the barrel, which is insufficient to permit automated assembly of the whole unit. When, in this configuration, the second central end of the spring is hooked or fixed to a core which pivots about a fixed arbour integral with the bottom plate and/or barrel bar, it is possible to remove the barrel by dismantling fewer components of the movement than in the preceding case where the cover is fixed to the drum and independent of the ratchet.
In both the first and second case, under the effect of accelerations and particular in the event of a shock, the barrel is liable to move away from its pivoting points, and no longer be able to perform the function of driving the movement to which it is dedicated.
DE Utility Model 18 72 388 U in the name of EPPLE KG OTERO UHREN discloses a barrel with an internally threaded socket pivoting in a bar and carrying a ratchet pivoting integrally therewith. This socket includes an external groove which cooperates with a strip spring fixed to said bar and abutting on the bottom plate. The internal threading of the socket acts as a housing for a barrel arbour which includes: a bottom shoulder pivoting in the bottom plate, a median cylindrical shoulder pivoting in a core which abuts on the socket, a thread cooperating with the internal threading of the socket, and a top head which holds the ratchet on the socket. The core has two shoulders, one acting as a support for the drum and the other for the cover. A first core limiting surface, which is the surface abutting on the drum, and a second core stopping surface, which is the surface abutting on the socket, form a limit in the same direction of movement of the core.
CH Patent Application No. 158 295 A in the name of AMIDA discloses a barrel with a drum including external hooking lugs limiting the expansion of the spring. The drum is pressed onto a ring, and a minute wheel and a small wheel can slide onto a shoulder of the ring, in which the barrel arbour pivots, limited by a circlip. The arbour is limited in this case by two opposite stop members: the circlip, and the top shoulder whose diameter is larger than the arbour, on either side of the ring. The drum, integral with the ring, is imprisoned between the two stopping surfaces of the core.
U.S. patent application Ser. No. 389,852 A in the name of MOULTON discloses a barrel for a clock, without a drum, but with a fixed frame which includes a fixed hooking point for the outer end of the spring.
FR Patent Application No 1 042 548 A in the name of PARRENIN LANGE discloses a removable barrel, rotatably mounted about a hollow arbour which contains a removable pin, which pivots integrally therewith but is free to move in translation, said pin including a means of driving the ratchet.